Drove up to Evergreen yesterday and tried out the JazzAmp, and I'm pretty impressed. (FWIW, my only real frame of reference is the Contra I've been using for the past several years, plus what I've seen/heard around town.)
The thing puts out a lot more clean sound than the Contra, it's comparably compact in size, and I believe it's a pound or two lighter. Looks/feels well made. It took a little fiddling to get the sound I like -- had to EQ out some mids and boost the highs a bit -- but what I wanted seemed to be well within its reach.
My only real complaint with the Contra has been a lack of power/headroom in certain situations, and I think the JazzAmp would be an effective solution. (Plus, if I drove one off the "line out" of the other, I'd have a LOT of sound!)
At the $749 "introductory" price, it's looking pretty appealing. I'll probably take the plunge.
FWIW,
Mark